LONDON, England (CNN) -- The worst snowstorm to hit Britain in 18 years forced the cancellation of more than 650 flights at London's Heathrow airport Monday and shut down the city's bus network, partially paralyzing the British capital.

A group of men push a giant snowball across Kensington Gardens, west London Monday.

Heathrow, one of the busiest transport hubs in the world, closed both its runways for more than two hours Monday morning and operated with just one for the rest of the morning, according to BAA, the company which runs it.

London City airport is also closed, while the British capital's other two airports, Stansted and Gatwick, were operating with severe delays, BAA said.

One of the city's largest cab companies was in such high demand it stopped taking cash and credit card bookings, serving only customers with accounts, it said.

Dial-a-Cab, which has a fleet of over 2,500 vehicles, served mainly blue-chip companies trying to get employees into work, said Keith Cain a Control Room manager for the company. Customers waited up to an hour and a half for a cab early in the morning, he said. See gallery of UK under snow »

Jochen Jaeger, 36, found himself stranded at Heathrow, unable to fly home to Zurich or to get back into the apartment he rented in London.

"I will stay here at the airport," he told CNN. "There is no other option. I may have to spend the night here."

American businessman Ken Plunkett, 60, from St. Paul, Minnesota, was trying to fly out from Heathrow Airport but found himself caught in the weather chaos. "I know England does not have the infrastructure to remove snow like we do in Minnesota," he said.Watch passenger stranded by snow »

Jenny Leslie, a shop worker at Heathrow's Terminal 2, said it was so quiet at the airport "you can hear a pin drop."

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Southampton Airport, southwest of London, was also closed for several hours Monday morning, but re-opened by 1200 GMT.

But many people in the city were delighted by the unusual weather.

"Londoners of all ages are childishly happy to be making snowmen and having snowball fights. Bankers of all ages are throwing snowballs in the middle of the residential streets," Monica Majumdar told CNN in an iReport.

She lived in New York before moving to London four years ago, and was surprised by how little snow it took to bring the British capital to a standstill.

"I have seen snow like this. But somehow, it's more beautiful here. It's partly due to the fact that even Londoners are amazed by the snow -- so there is a general air of surrealism," she said via e-mail. " I do feel like I'm in a Christmas snowglobe, with all the iconic London monuments blanketed by the powdered snow."

London's famous red buses were pulled off the roads on Sunday night as the snow got deeper.

It was the first time "in living memory" that all city bus service had been suspended, including when London was being bombed during World War II, a spokesman for the city's transit agency, Transport for London, said.

"Bus services were suspended throughout London last night on the grounds of passenger safety due to the unsafe road conditions resulting in a large number of traffic incidents across London," the agency said in a statement Monday morning. Watch London grind to a halt »

About six million people ride London buses each day, said the spokesman, who asked not to be named.

Some bus service had been restored by lunchtime on Monday.

London Mayor Boris Johnson suspended the £8 ($11.30) daily congestion charge drivers normally pay to enter central London, the city transport authority said. Some bus service had been restored by lunchtime on Monday.

The city's subway system was also experiencing severe delays, leaving normally bustling central London something of a ghost town.

On a regular weekday, London's transit system handles more than three million passenger journeys.

The Federation of Small Businesses estimated that at least one in five workers nationwide -- about 6.4 million employees -- failed to make it into work Monday morning.

The snow meant a break from school for the region's children as classes gave way to snowball fights.

In the southern English seaside resort of Brighton there was a carnival atmosphere as dozens of people who were unable to get to work threw snowballs and built snowmen on the beach.

Mother-of-three Fiona Robbins, 45, added: "Everyone is very excited to be able to show their children proper snow for the first time."

Tuesday's forecast is expected to bring some relief, with the snow expected to stop and temperatures to rise above freezing.

Two climbers were found dead Monday morning on Snowdon, the highest mountain in Wales, after being reported missing Sunday night, North Wales Police said. It was not clear if their deaths were related to the storm.